A nightmare is the strongest example of what reality dream life can apparently attain. Suppose for a minute that one's own body has become the imagined body belonging to one in a vivid dream. During the period of dream, men may gash it with knives and stab it with daggers. The skin will be cut, the flesh penetrated, the nerves severed; pain will be felt, and blood will pour out of this body. All may happen during such a horrible nightmare precisely as it may happen during the waking state and with the same dramatic vividness. Yet during the whole ghastly experience the skin, nerves, flesh, and blood were merely imagined, were only ideas! The whole apparatus of sense, whether it be eye or ear or skin, and the whole mechanism of nerves, are themselves mental experiences no less than those dream ideas and those dream perceptions which we unhesitatingly accept as such.
-- Notebooks Category 19: The Reign of Relativity > Chapter 3 : The States of Consciousness > # 48
